Известно, что tg(a-п/4)=6, найдите 10 tg a

tg(a-\frac{\pi}{4})= \frac{tga-tg\frac{\pi}{4}}{1+tga\cdot tg\frac{\pi}{4}} = \frac{tga-1}{1+tga} =6\; \; \Rightarrow\\\\tga-1=6\cdot (tga+1)\\\\tga-1=6tga+6\\\\5tga=-7\\\\tga=-\frac{7}{5}\\\\10tga=-\frac{70}{5}=-14